The present invention relates to Semaphorin Y, a novel Semaphorin belonging to the Semaphorin family, and use of Semaphorin Y for pharmaceutical or diagnostic agents or laboratory reagents. More particularly, it relates to Semaphorin Y inhibiting neurite outgrowth, and a gene therefor, as well as other Semaphorins hybridizing to said Semaphorin Y gene, modified proteins or partial peptides of said Semaphorin Y, antibodies against said Semaphorin Y, antisense nucleotides against said Semaphorin Y gene, antagonists of said Semaphorin Y, transgenic animals, and their use as pharmaceutical or diagnostic agents or laboratory reagents.
It is widely known that a central nervous system (CNS)-neuron in higher organisms such as human is not capable of regeneration once injured. Therefore, one who has received an injury on his (her) spinal cord due to, for example, a traffic accident, is compelled to spend the rest of his (her) life in a hemiplegic state. On the contrary, it is known that a peripheral nervous system (PNS)-neuron retains a vigorous regeneration ability even in those higher organisms, and therefore, neurons in a limb, when disconnected, can gradually regenerate with a concomitant recovery of their function.
In the early nineteen eighties, a group of Aguayo et al. found that when PNS-neuron is experimentally grafted into an injured CNS-neuron in a higher organism, axon growth of CNS-neuron is induced. This observation demonstrates that CNS-neuron in higher organisms which had been generally considered not to have a regeneration ability can regenerate if a suitable environment is provided (Nature, 284, 264-265 (1980), Science, 214, 931-933 (1981)). That report suggests a possibility that in CNS of higher organisms, there may exist a factor, namable xe2x80x9cCNS-neuron regeneration inhibitorxe2x80x9d, which inhibits the regeneration of CNS-neuron, and that a release from such inhibition may allow the regeneration of CNS-neurons. This suggestion paved the way for a CNS-neuron regeneration therapy.
In 1988, a group of Schwab et al. demonstrated that there exited such CNS-neuron regeneration inhibitor among proteins derived from CNS myelin. They also succeeded in purifying, though partially, a protein having said CNS-neuron regeneration inhibition activity, and named this protein fraction NI35/250 (Annu. Rev. Neurosci., 16, 565-595 (1993)), although no one has succeeded in its isolation, identification and gene cloning yet. In addition, they immunized animals with the partial purified NI35/250, and succeeded in obtaining an antibody (IN-1) having a neutralizing activity. This antibody is capable of recognizing a band for NI35/250 in Western blotting, and capable of staining, in an immunostaining, the region to which NI35/250 is supposed to be distributed. Furthermore, they demonstrated that administration of this antibody to an animal experimentally received an injury on its spinal cord has promoted regeneration of axons in spinal cord, though partially, within 2-3 weeks, and restored its function within 2-3 months (Nature, 343, 269-272 (1990), Nature, 378, 498-501 (1995)). These findings are of great value, because they experimentally demonstrated that there existed a CNS-neuron regeneration inhibitor as suggested by Aguayo et al. (supra) and that CNS-neuron can be regenerated by inhibiting the activity of said inhibitor. The above antibody is, however, directed not to human but to rat NI351/250, and exhibits a low stability and specificity. In addition, although regeneration of CNS-neuron was observed as described above by administering said antibody, its effect was so partial and incomplete that not all of the motor functions could be restored. It is, therefore, believed essential in solving these problems to identify the gene for NI35/250 or corresponding CNS-neuron regeneration inhibitor, and, based on knowledges of molecular biology, neuroscience and the like, develop an antagonist more effectively inhibiting the CNS-neuron regeneration inhibition activity, or develop a method for inhibiting the expression of the gene for said regeneration inhibitor.
Apart from the above, the nervous system, whether it is central or peripheral, requires formation of a complicated neural network among neurons or between neurons and peripheral receivers or effectors during development, that is, in the stage of embryo or fetus, in order to precisely carry out its principal functions, i.e., to transfer and process the information. To establish the neural network, an ingenious mechanism is necessary, which precisely guides a growing neurite to the target site locating remote therefrom.
It has been hitherto believed that a factor which positively controls the neurite outgrowth, such as neurite growth promoter and neurite growth attractant may play a major role in the formation of the neural network. However, it is now being demonstrated by recent studies on the mechanism of the network formation that the opposite factor, that is, a negative factor having an outgrowth inhibition activity is important for an accurate guidance (Cell, 78, 353-356 (1994)).
A representative factor having such an outgrowth inhibition activity is a protein called xe2x80x9cSemaphorinxe2x80x9d. Semaphorin firstly discovered is Fasciclin IV found in grasshopper. Collapsin (latterly named Collapsin I) was subsequently discovered in chick (Cell, 75, 217-227 (1993); Neuron, 9, 831-845 (1992)). To date, more than 10 genes belonging to the Semaphorin family have been reported in a wide range of species covering insects such as drosophila and beetle, human, and viruses (Cell, 81, 471-474 (1995)). These Semaphorins characteristically contain in their amino acid sequences similar structures called semaphorin domains each consisting of about 500 amino acids (Neuron, 14, 941-948 (1995); Cell, 75, 1389-1399 (1993)). However, the homologies of the primary amino acid sequences in semaphorin domains among these Semaphorin genes are 80-20%, and not necessarily high.
Of these Semaphorins, functions have been verified for only a few, including, for example, Fasciclin IV of grasshopper, Semaphorins I and II of drosophila, Collapsin of chick, and Semaphorin III which corresponds to Collapsin in mammals. All of these Semaphorins are known to inhibit neurite outgrowth or synapsis formation. In particular, Semaphorin III has been reported to have an activity collapsing in a short time the growth cone of cultured neuron (growth-cone collapse activity) in vitro (Neuron, 14, 941-948 (1995); Neuron, 14, 949-959 (1995); Cell, 81, 631-639 (1995); Cell, 75, 1389-1399 (1993); Cell, 14, 217-227 (1993); Neuron, 9, 831-845 (1992)).
Although it is now being demonstrated, as described above, that known Semaphorins have a growth-cone collapse activity and a neurite outgrowth inhibition activity during development, and play a role in giving an accurate guidance to neuron, it is not evident at present whether or not their Semaphorins exert some function not only during development but also in the adult, and less evident whether or not Semaphorins play a role as a CNS-neuron regeneration inhibitor. Of course, since known Semaphorins have been shown to be a negative guidance factor inhibiting neurite outgrowth, it would not be unreasonable to consider said Semaphorins as a candidate for a CNS-neuron regeneration inhibitor (Nature, 378, 439-440 (1995)). However, it has been shown by in vitro experiments that Semaphorin III (Sema III), only one Semaphorin of higher organisms of which function has been analyzed, exerts its neurite-outgrowth inhibition activity on a sensory neuron and sympathetic neuron both of which are peripheral, but not on a retinal neuron which is central (Cell, 75, 217-227 (1993)). In addition, Northern analysis on the distribution of Sema III expression in the adult conducted by the present inventors has revealed that it is expressed mainly in peripheral tissues (see Reference example 2 below). It is therefore hardly believed that Sema III having such features has a function as a CNS-neuron regenen inhibitor.
The present invention aims to provide Semaphorin Y, a novel Semaphorin belonging to the Semaphorin family, and a gene therefor, and to provide pharmaceutical agents for neural diseases, in particular for regeneration of CNS-neuron, and related diagnostic agents or laboratory reagents. More specifically, the present invention aims to provide Semaphorin Y inhibiting neurite outgrowth and a gene therefor, as well as other Semaphorins hybridizing to said Semaphorin Y gene, modified proteins or partial peptides of said Semaphorin Y, antibodies against said Semaphorin Y, antisense nucleotides against said Semaphorin Y gene, and use of such substances as pharmaceutical or diagnostic agents or laboratory reagents. The present invention further aims to provide a method of screening for Semaphorin Y antagonists empolying said Semaphorin Y, Semaphorin Y antagonists obtained by said screening method, pharmaceutical agents comprising such antagonists, and transgenic animals involving Semaphorin Y.
In order to provide pharmaceutical agents for neural diseases, in particular for regeneration of CNS-neuron, and related diagnostic agents or laboratory reagents, the present inventors have planed to identify a novel Semaphorin which has not yet been cloned. In particular, the present inventors have paid their attention to the similarity between the in vitro activities of the above-described NI35/250 and Semaphorin, i.e., to the fact that NI35/250 has a growth-cone collapse activity and a neurite-growth inhibition activity in vitro (J. Neurosci., 8, 2381-2393 (1988); Science, 259, 80 (1993)), while known Semaphorins similarly possess a neurite-growth inhibition activity, and particularly Semaphorin III has also a growth-cone collapse activity. This suggested to the inventors the possibility that unknown Semaphorins which have not yet been identified may include the one inhibiting regeneration of CNS-neuron. Specifically, the present inventors"" idea was that Semaphorin, which is characterized in that 1) it is widely expressed throughout the CNS of adult where regeneration of neuron (or neurite outgrowth) is inhibited, but 2) it is poorly expressed in other tissues such as peripheral tissues in the adult, has not been identified yet, and if one can identify a new unknown Semaphorin having such characteristics, the Semaphorin might be involved in inhibition of regeneration of CNS-neuron.
First of all, the inventors have closely searched DNA database on the basis of the amino acids sequence relatively well conserved among previously reported Semaphorin genes. Specifically, a DNA sequence has been searched through EST (Expressed Sequence Tags) database, which is a gene not expressed in peripheral tissues but expressed in the postnatal brain and which encodes an amino acid sequence relatively well conserved among Semaphorins. As a consequence, a DNA fragment R59527 (referred to in the sequence listing as SEQ ID NO: 12, here and after referred to as xe2x80x9cR59527xe2x80x9d) was identified, which encodes, as a partial sequence, a sequence consisting of seven amino acids: Gln (or Arg)-Asp-Pro-Tyr-Cys-Ala (or Gly)-Trp (SEQ ID NO: 12). The R59527 gave a sequence information as to only 238 bases, and furthermore only several percent thereof could be translated into an amino acid sequence common to those of known Semaphorins. In addition, the reading frame could not be determined because of the presence of sequence not definitely determined in R59527. It was, therefore, utterly impossible at that stage to conclude that the base sequence of R59527 is part of a novel Semaphorin. We have, however, finally succeeded in cloning a novel Semaphorin gene by carrying out the following procedures: synthesizing DNA primers on the basis of that sequence information; conducting PCR with said primers using cDNAs prepared from a human hippocampal cDNA library as templates to obtain a novel DNA fragment (SEQ ID NO: 7) consisting of 170 bases; labeling the DNA fragment with 32P to synthesize a DNA probe; and screening rat and human cDNA libraries with that probe. We named this novel Semaphorin xe2x80x9cSemaphorin Yxe2x80x9d.
Subsequent analysis revealed that Semaphorin Y is a novel Semaphorin at which we aimed, since it was widely expressed in CNS in the adult, whereas among peripheral tissues the expression could be observed only in limited tissues.
Semaphorin Y of the present invention having such characteristics appears to be involved in inhibition of regeneration of CNS-neuron in the adult. Semaphorin Y may be used to screen for Semaphorin Y antagonists, and antagonists identified in such screening system are expected to promote regeneration of CNS-neuron. Similarly, antisense DNAs or RNAs against Semaphorin Y gene are also expected to promote regeneration of CNS-neuron as the above antagonists do.
In addition, in view of the fact that Semaphorin Y of the present invention inhibits neurite outgrowth, it may be used as a therapeutic or diagnostic agent for pains or immune diseases such as atopic dermatitis, by administering it to peripheral tissues, which results in the inhibition of neurite outgrowth of PNS-neuron. Furthermore, Semaphorin Y is a novel Semaphorin belonging to the Semaphorin family of which expression distribution is unconventionally characteristic as described above, and also has a characteristic in that it does not contain any Ig domains commonly found among hitherto reported Semaphorins of vertebrates. Semaphorin Y may, therefore, serve as an important research material or a laboratory reagent.
The present invention has been completed on the basis of the above findings.
Thus, the gist of the present invention is as follows:
(1) a gene encoding the following protein (a) or (b):
(a) Semaphorin Y protein comprising the amino acid sequence shown in SEQ ID NO: 3 or 6,
(b) a protein which comprises an amino acid sequence wherein one or more amino acids are deleted, substituted and/or added in the amino acid sequence shown in SEQ ID NO: 3 or 6, and which protein inhibits neurite outgrowth;
(2) a gene comprising the following DNA (a) or (b):
(a) Semaphorin Y DNA comprising the base sequence shown in SEQ ID NO: 1, 2, 4, or 5,
(b) DNA which hybridizes under stringent conditions to DNA comprising the base sequence shown in SEQ ID NO: 1, 2, 4, or 5, and which encodes a protein inhibiting neurite outgrowth;
(3) a gene comprising DNA which hybridizes under stringent conditions to DNA comprising the base sequence shown in SEQ ID NO: 7, and which encodes a protein having a semaphorin domain;
(4) a protein obtained by expressing the gene of any one of the above items (1) to (3);
(5) a gene comprising DNA which encodes a protein comprising an amino acid sequence in which one or more amino acids are deleted, substituted and/or added in the protein shown in SEQ ID NO: 3 or 6, wherein said protein promotes neurite outgrowth;
(6) a protein obtained by expressing the gene of the above item (5);
(7) DNA which is cloned from a human cDNA library or a human genomic library, and which hybridizes under stringent conditions to DNA comprising at least part of DNA consisting of the base sequence shown in SEQ ID NO: 1 or 4;
(8) an expression plasmid which expresses either the gene of any one of the above items (1) to (3) and (5), or DNA of the above item (7);
(9) a transformant transformed with the expression plasmid of the above item (8);
(10) a process for producing a recombinant protein, which process comprises culturing the transformant of the above item (9), and recovering the recombinant protein expressed;
(11) a peptide comprising at least six amino acids of the protein of the above item (4) or (6);
(12) a peptide of the above item (11) which promotes neurite outgrowth;
(13) a peptide of the above item (11) characterized in that it contains aspartic acid residue at position 198 of the amino acid sequence shown in SEQ ID NO: 6 or an amino acid residue corresponding to the position of said aspartic acid residue;
(14) an antisense nucleotide, or chemically modified variant thereof, which is directed against a segment comprising at least eight or more bases in the gene of any one of the above items (1) to (3), or in DNA of the above item (7);
(15) an antisense nucleotide or chemically modified variant thereof of the above item (14), characterized in that it inhibits expression of the protein of the above item (4);
(16) an antibody against the protein of the above item (4) or (6), or against the peptide of any one of the above items (11) to (13);
(17) a pharmaceutical agent comprising, as an active ingredient, the gene of any one of the above items (1) to (3) and (5), DNA of the above item (7), the protein of the above item (4) or (6), the peptide of any one of the above items (11) to (13), the antisense nucleotide or chemically modified variant thereof of the above item (14) or (15), or the antibody of the above item (16);
(18) a method of screening for Semaphorin Y antagonists, characterized in that it employs the protein of the above item (4);
(19) Semaphorin Y antagonist obtained by the screening method of the above item (18);
(20) Semaphorin Y antagonist of the above item (19) which comprises the protein of the above item (6), the peptide of any one of the above items (11) to (13), or the antibody of the above item (16);
(21) a CNS-neuron regeneration promoter, characterized in that it contains at least one of the antisense nucleotides or chemically modified variants thereof of the above item (14) or (15), or Semaphorin Y antagonists of the above item (19) or (20);
(22) a neurite outgrowth inhibitor for PNS-neuron, characterized in that it contains at least one of the proteins of the above item (4); and
(23) a transgenic animal in which either the gene of any one of the above items (1) to (3) and (5), or DNA of the above item (7) has been artificially inserted into its chromosome, or has been knocked out.
The 1st embodiment of the present invention is a gene which encodes Semaphorin Y comprising the amino acid sequence shown in SEQ ID NO: 3 or 6, or a gene encoding a protein which comprises an amino acid sequence wherein one or more amino acids are deleted, substituted and/or added in the amino acid sequence of the above Semaphorin Y, and which protein inhibits neurite outgrowth. The 2nd embodiment of the present invention is Semaphorin Y gene comprising the base sequence shown in SEQ ID NO: 1, 2, 4, or 5, or a gene which hybridizes under stringent conditions to such Semaphorin Y gene and which encodes a protein inhibiting neurite outgrowth. These genes are explained below in order.
1) Gene Encoding Semaphorin Y (Semaphorin Y Gene)
Of the above-mentioned genes, xe2x80x9ca gene which encodes Semaphorin Y protein comprising the amino acid sequence shown in SEQ ID NO: 3xe2x80x9d or xe2x80x9cSemaphorin Y gene comprising the base sequence shown in SEQ ID NO: 1 or 2xe2x80x9d is a gene encoding the rat Semaphorin Y of the present invention, while xe2x80x9ca gene which encodes Semaphorin Y protein comprising the amino acid sequence shown in SEQ ID NO: 6xe2x80x9d or xe2x80x9cSemaphorin Y gene comprising the base sequence shown in SEQ ID NO: 4 or 5xe2x80x9d is a gene encoding the human Semaphorin Y of the present invention. Among these genes, those shown in SEQ ID NOs: 2 and 5 correspond open reading frames for rat and human types of Semaphorin Y, respectively. Such genes may be cloned, as described in Example 1, by screening a cDNA library derived from CNS tissues using a probe (for example, a DNA probe having the base sequence shown in SEQ ID NO: 7) prepared on the basis of the sequence of xe2x80x9cR59527xe2x80x9d found in EST database. Particular techniques for such cloning may be found in the standard texts such as xe2x80x9cMolecular Cloning, 2nd ed.xe2x80x9d, Cold Spring Harbor Laboratory Press (1989). The base sequence of the cloned DNA may also be determined by conventional methods, for example, using a sequencing kit commercially available.
Alternatively, after publication of the base sequence of rat and human Semaphorin Y cDNAs of the present invention, one skilled in the art can also easily clone the full-length genes encoding rat and human types of Semaphorin Y by using part of said cDNA as a probe, without using cloning methods as described above.
2) Gene Encoding Modified Protein of Semaphorin Y
Of the above-mentioned genes, xe2x80x9ca gene encoding a protein which comprises an amino acid sequence wherein one or more amino acids are deleted, substituted and/or added in the amino acid sequence of the above Semaphorin Y, and which protein inhibits neurite outgrowthxe2x80x9d refers to a gene encoding a so-called xe2x80x9cmodified proteinsxe2x80x9d of Semaphorin Y which inhibits neurite outgrowth. Those skilled in the art may easily obtain a gene encoding such protein, for example, by site-directed mutagenesis (Methods in Enzymology, 100, 448- (1983)) or PCR method (Molecular Cloning, 2nd ed., Chapter 15, Cold Harbor Laboratory Press (1989); xe2x80x9cPCR A Practical Approachxe2x80x9d, IRL Press, 200-210 (1991)). In this context, the number of amino acid residues to be deleted, substituted and/or added is to be such a number that permits the deletion, substitution and/or addition by well-known methods such as site-directed mutagenesis described above.
For the purpose of the present invention, the phrase xe2x80x9cinhibiting neurite outgrowthxe2x80x9d means that the protein has the collapse activity on growth cone of neuron, or that the protein has the neurite-outgrowth inhibition activity. These activities may be measured with a test substance such as an expression product of DNA encoding Semaphorin Y or modified protein thereof, for example, in the following manner:
Since Semaphorin Y is a membrane protein, it exists in the cell membrane of the cells transformed with Semaphorin Y gene. The activities of the above test substance may, therefore, easily be measured by using, as a test material, the membrane fraction of the transformed cells.
Examples of activity measurement include measurement of collapse activity on growth cone of neuron (M. Igarashi et al., Science, vol. 259, pp. 77-79 (1993)), or measurement of neurite-outgrowth inhibition activity (e.g., J. A. Davies et al., Neuron, vol. 2, pp. 11-20 (1990) and M. Bastmeyer, J. Neurosci., vol. 11, pp. 626-640 (1991)). A method of measuring the growth-cone collapse activity is described in detail in literature (M. Igarashi et al., Science, vol. 259, pp. 77-79 (1993)). Briefly, the measurement may be carried out by a method in which cells expressing a test substance such as Semaphorin Y is homogenized, and the homogenate containing the cell membrane fraction or the purified membrane fraction is used (E. C. Cox et al., Neuron, vol. 2, pp. 31-37 (1990)), or by a method in which a protein extracted from the membrane fraction is reconstituted in a liposome and the liposome is used as a test material (C. E. Bandtlow, Science, vol. 259, pp. 80-84 (1993)). In order to measure the growth-cone collapse activity in practice using these materials, a test substance such as Semaphorin Y, for example, in one of the forms as describe above is added to neurons cultured under conventional conditions (e.g., xe2x80x9cCulturing, Nerve Cellsxe2x80x9d edited by Banker et al., MIT Press (1991)) in a container coated with a substance promoting the neurite outgrowth and the growth-cone formation such as laminin, collagen, polylysine or polyornithine. After the addition, when a sufficient time has passed to occur collapse of growth cone (typically from 30 minutes to one hour after the addition), those neurons are fixed with 1% glutaraldehyde or the like, and the number of the growth cones which have been collapsed is counted under a microscope. In this measurement, it is important that another sample is used as a control, which is prepared from cells not expressing the test substance such as Semaphorin Y according to the completely same procedures as those used for the test substance-expressing cells. Typically, normalization of the samples is conducted on the basis of the total amounts of protein included within the samples. To measure the neurite-outgrowth inhibition activity, part of the surface of a micropore filter or a culture container made of glass or plastics is coated with a test substance such as Semaphorin Y prepared as described above, and the activity is indicated, for example, by the inability of neurons cultured under conventional conditions to adhere to the coated area, or by a remarkable decrease in the rate of neurite outgrowth on the coated area, or by the inability of invasion of growing neurites from the outside of the coated area into the coated area because of its stopping on the border between the coated and non-coated areas or its avoidance from the coated area. When a cluster of cells expressing a test substance is co-cultured with neurons in a collagen gel, the inability of outgrowing neurite to enter the cluster of cells expressing the test substance may also be used as an indicator (A. Sophia et al., Cell, vol. 81, 621-629 (1995)).
Both neurons of CNS and PNS may be used as the cells for the above activity measurements. As described in the section xe2x80x9cBACKGROUND ARTxe2x80x9d, CNS in adult mammals naturally contains a large amount of regeneration (outgrowth) inhibitor. It is, therefore, extremely difficult to measure in vivo an inhibitory effect on neurite outgrowth of CNS-neuron, and such inhibitory effect is usually measured by an in vitro method as described above. Since these in vitro methods each have individual characteristics, it is preferred to use more than one method to confirm the activity. Although preferred neurons used for a measurement of the activity are CNS-neurons such as motor neurons in spinal cord or motor cortex, PNS-neurons in superior cervical ganglion and dorsal root ganglion may also be used because N135/250 known as a CNS-neuron regeneration inhibitor has proved to have effects such as neurite-growth inhibition and growth-cone collapse activities also on such PNS-neurons (J. Cell Biol., 106, 1281-1288 (1988); Science, 259, 80-83 (1993)).
Specific examples of the modified proteins of this embodiment are described below.
Based on the structural comparison of known Semaphorins, most of the conserved amino acids are located in the semaphorin domain, suggesting that these conserved amino acids are essential for expression of the activity of Semaphorins. Furthermore, the present inventors have found that a modified Sema III protein in which aspartic acid residue at position 198 in its semaphorin domain has been substituted with glycine did not have the growth-cone collapse activity (see Reference example 1 below). Accordingly, the aspartic acid at position 198 of Sema III is believed essential for expression of the activity. The amino acid residues corresponding to this position are highly conserved in known Semaphorins, and they are all aspartic acid with a few exceptions in which glutamic acid is located at this position. It is, therefore, believed that the amino acid residue at this position is also essential for expression of the activity of Semaphorins other than Sema III. In Semaphorin Y of the present invention, the amino acid residue corresponding to the position 198 of Sema III is presumed to be aspartic acid at position 197 in the amino acid sequence shown in SEQ ID NO: 3, or aspartic acid at position 198 in the amino acid sequence of human Semaphorin Y shown in SEQ ID NO: 6.
Considering the above information, it is desirable to make the above-described deletions, substitutions and/or additions of amino acids at positions other than those conserved among Semaphorins, so as to retain the activity of Semaphorin Y in modified proteins. Particularly, it is desirable not to modify the aspartic acid at position 197 in rat Semaphorin Y shown in SEQ ID NO: 3 and the aspartic acid at position 198 in human Semaphorin Y. In order to substitute amino acids conserved among Semaphorins while retaining the activity of Semaphorin Y, it is desirable to substitute an amino acid having a similar side chain for the amino acid residue to be substituted. By substituting such amino acid having a similar side chain for a conserved amino acid, it may be possible to produce a modified protein which has an enhanced activity of Semaphorin Y. Such modified protein having the enhanced activity is highly suitable as a neurite-outgrowth inhibitor for PNS-neuron as will be described hereinafter in the section of the 22nd embodiment of the present invention.
In the above-noted embodiment, xe2x80x9ca conserved amino acidxe2x80x9d refers to an amino acid located at a position at which more than 50% of Semaphorin genes shown in FIG. 2 of Cell, 75, 1389-1399 (1993) or FIG. 1 of Neuron, 14, 941-948 (1995) share the same amino acid.
3) DNA Hybridizing Under Stringent Conditions to Semaphorin Y Gene
Of the above-mentioned DNAs, xe2x80x9ca gene which hybridizes under stringent conditions to Semaphorin Y gene and which encodes a protein inhibiting neurite outgrowthxe2x80x9d refers to a gene such as Semaphorin Y gene derived from a mammal, which hybridizes under stringent conditions to rat or human Semaphorin Y gene comprising the base sequence shown in SEQ ID NO: 1, 2, 4, or 5.
As used herein, xe2x80x9ca gene which hybridizes under stringent conditionsxe2x80x9d refers to such a gene that hybridizes to rat or human Semaphorin Y gene, for example, when subjected to hybridization at a formamide concentration of about 45% (v/v) and a salt concentration of about 5xc3x97 SSPE and at a temperature around 42xc2x0 C., and washed at a salt concentration of about 2xc3x97 SSPE and at a temperature around 42xc2x0 C. Cloning of such genes may be achieved, for example, by screening cDNA or genomic libraries prepared from various animal tissues using all or part of DNA shown in SEQ ID NO: 1 or 4 as a probe. Such screening may be carried out by making reference to the standard texts such as xe2x80x9cMolecular Cloning 2nd ed.xe2x80x9d (Cold Spring Harbor Laboratory Press (1989)).
Specific examples of the gene of this embodiment may include all the Semaphorin Y genes of mammal and avian. Between mammals or between mammal and avian, homologous genes have quite similar sequences, and usually more than 80%, in many cases more than 90%, of the base sequence are common to each other. All the mammal and avian Semaphorin Y genes, therefore, correspond to this embodiment. In other words, those genes which have a homology of 80% or above, and preferably of 90% or above, are included in this embodiment.
The 3rd embodiment of the present invention is a gene comprising DNA which hybridizes under stringent conditions to DNA comprising the base sequence shown in SEQ ID NO: 7, and which encodes a protein having a semaphorin domain.
In the above description, xe2x80x9cDNA comprising the base sequence shown in SEQ ID NO: 7xe2x80x9d refers to a fragment cloned by PCR using the sequence information of the DNA xe2x80x9cR59527xe2x80x9d which encodes, in part, a sequence consisting of seven amino acids well conserved among Semaphorins (Gln (or Arg)-Asp-Pro-Tyr-Cys-Ala (or Gly)-Trp (SEQ ID NO: 12)), and the DNA fragment corresponds to a region from position 1574 to position 1743 in the base sequence of rat Semaphorin Y shown in SEQ ID NO: 1, or a region from position 1524 to position 1693 in the base sequence of human Semaphorin Y shown in SEQ ID NO: 4.
The xe2x80x9cstringent conditionsxe2x80x9d refers to those conditions described above in the section of the 2nd embodiment of the present invention.
Cloning of these DNAs is achieved by, for example, hybridization with DNA of SEQ ID NO: 7, and specifically may be carried out, for example, according to the procedures described in TINS, 15, 319-323 (1992) and references cited therein, and more specifically according to the following procedures.
That is, the cloning may be achieved by screening cDNA or enomic libraries prepared from various animal tissues using DNA consisting of the base sequence shown in SEQ ID NO: 7 as a probe. The screening may be carried out according to, for example, the procedures as described in Example 1. Preferred cDNA libraries are those derived from an adult tissue of CNS, and cDNA libraries derived from hippocampus,.corpus striatum, and cerebellum are more preferred. As described above, the conditions shown in Example 1 or those described in TINS, 15, 319-323 (1992) and references cited therein may be used for the hybridization.
The DNA of this embodiment is also xe2x80x9cDNA which encodes a protein having a semaphorin domainxe2x80x9d. As used herein, xe2x80x9csemaphorin domainxe2x80x9d refers to a domain consisting of 300-600 amino acid residues more than 20% of which are identical to those amino acids constituting the semaphorin domain of any one of ten known Semaphorins (G-Sema I, T-Sema, I, D-Sema II, H-Sema III, C-Collapsin, Sem A, Sem B, Sem C, Sem D, Sem E) described in, for example, Cell, 75, 1389-1399 (1993) or Neuron, 14, 941-948 (1995). Those proteins having a semaphorin domain more than 30% of which amino acids are identical to those amino acids in any one of the known Semaphorins are particularly preferred. The identity of amino acids is determined by comparison using, for example, DNASIS Ver. 2.0 (HITACH Software Engineering) under conditions of ktup=1 and cutoff=1. More preferred proteins are those in which ten or more cysteines, particularly twelve or more cysteines, of the thirteen cysteines conserved in semaphorin domains of the ten known Semaphorins (for example, those cysteines marked in FIG. 1 on page 942 of Neuron, 14, 941-948 (1995)) are conserved.
Examples of such gene of this embodiment may include Semaphorin genes which hybridize under stringent conditions to DNA comprising the base sequence shown in SEQ ID NO: 7 and which contain semaphorin domains and exhibit the neurite-outgrowth inhibition activity, including all of the Semaphorin Y genes of mammal and avian.
The 4th embodiment of the present invention is a protein obtained by expressing the gene of any one of the above items (1) to (3).
Typical examples of protein included in this embodiment are rat Semaphorin Y comprising the amino acid sequence shown in SEQ ID NO: 3, and human Semaphorin Y comprising the amino acid sequence shown in SEQ ID NO: 6. The rat or human Semaphorin Y contains a signal sequence at its N-terminus and such signal sequence is presumed to correspond to a region from position 1 to position 23 of the amino acid sequence shown in SEQ ID NO: 3 or from position 1 to position 24 of the amino acid sequence shown in SEQ ID NO: 6, respectively. Since the signal sequence is removed by processing during its transfer to membrane, such mature forms of Semaphorin Y are also included in this embodiment.
Preparation of the proteins of this embodiment may be achieved, for example, by ligating a cloned rat Semaphorin Y cDNA into a known expression vector such as pET or pCDM8, and introducing it into appropriate host cells to express and produce Semaphorin Y. The host cells may be prokaryotic or eukaryotic. For example, Escherichia coli strains or animal cell lines are already conventionally used for such purpose and are commercially or publicly available. Examples of animal host cells include COS-1, COS-7, CHO cells and the like.
To transform appropriate animal host cells with an expression plasmid, a known procedure such as DEAE-dextran method (Current Protocols in Molecular Biology, F. M. Ausubel et al. ed., John Wiley and Sons (1987)) may be used. As confirmed in Example 6, Semaphorin Y exists in the cell membrane faction which contains a sufficient amount of Semaphorin Y to be directly used in various assays. Therefore, various assays for activities of a protein of this embodiment may easily be conducted using a cell membrane fraction prepared from appropriate cells.
Furthermore, a protein of this embodiment may be purified by, for example, affinity purification using Semaphorin Y-recognizing antibodies described hereinafter in the section of the 16th embodiment of the present invention, or conventional column chromatography.
The 5th embodiment of the present invention is a gene encoding a protein which comprises an amino acid sequence wherein one or more amino acids are deleted, substituted and/or added in the rat or human Semaphorin Y shown in SEQ ID NO: 3 or 6 and which protein promotes neurite outgrowth. The 6th embodiment of the present invention is a protein obtained by expressing the gene of the 5th embodiment of the present invention.
In the genes of the above 5th embodiments, deletions, substitutions and/or additions may be introduced in the procedures similar to those used for a gene encoding a modified protein of the 1st embodiment of the present invention. Similarly, the pro motion effect on neurite outgrowth may easily be measured, for example, by adding Semaphorin Y in an assay system for Semaphorin Y activity described above in the section of the 1st embodiment of the present invention and further adding thereto a test substance (i.e., a candidate modified Semaphorin Y protein). For details, see the descriptions in the section of the 18th embodiment of the present invention.
Specific examples of the proteins of the 6th embodiment may be modified proteins of which neurite-outgrowth inhibition activity has been eliminated. Such modified protein lacking the neurite-outgrowth inhibition activity is expected to exert the promotion effect on neurite-outgrowth, when it binds to receptors for Semaphorin Y or to Semaphorin Y itself, by inhibiting the binding of Semaphorin Y to the receptors. As described above in the section of the 1st embodiment of the present invention, it has been suggested that the active site of Semaphorin may be located in the semaphorin domain, and particularly, it may be located at aspartic acid at position 197 in rat Semaphorin Y or aspartic acid at position 198 in human Semaphorin Y. Accordingly, in order to eliminate the semaphorin Y activity from the modified protein, it is desirable to introduce the deletions, substitutions and/or additions to the conserved amino acids in said semaphorin domain, preferably to the aspartic acid at position 197 in rat Semaphorin Y or to the aspartic acid at position 198 in human Semaphorin Y. In such cases, those substitutions in which an amino acid having a side chain of a distinct nature is substituted for the original amino acid are desirable. Also in the cases of Semaphorin Y other than that from human or rat, modifications are preferably made on aspartic acid at this position, that is, on amino acid residue at the position which corresponds to position 197 in rat Semaphorin Y or to position 198 in human Semaphorin Y when the amino acid sequence of said Semaphorin Y is aligned with that of rat or human Semaphorin Y so as to give the maximum identity.
Since the proteins of the 6th embodiment of the present invention promote neurite outgrowth as described above, some of these proteins will serve as CNS-neuron regeneration promoters as described hereinafter in the section of the 21st embodiment.
The 7th embodiment of the present invention is DNA which is cloned from a human cDNA library or a human genomic library, and which hybridizes under stringent conditions to DNA comprising at least part of rat or human Semaphorin Y DNA shown in SEQ ID NO: 1 or 4, respectively.
Methods of cloning are described in detail in, for example, xe2x80x9cMolecular Cloning 2nd ed.xe2x80x9d, Cold Spring Harbor Laboratory Press (1989), and specifically include, for example, methods employing hybridization or PCR. Although a preferred library used herein is a genomic library derived from human, a cDNA library derived from CNS-neuron in the adult may also be used. Those methods employing hybridization may be carried out according to, for example, TINS, 15, 319-323 (1992) and references cited therein. Those methods employing PCR may be carried out according to, for example, xe2x80x9cPCRxe2x80x9d edited by McPherson et al., IRL Press (1991).
The DNAs thus cloned include not only the full length DNA but also its DNA fragments comprising more than 200 bases, or single-stranded forms (coding strands or complementary stands thereof) of said DNA fragments. Specific examples of DNA of the 7th embodiment of the present invention may include chromosomal DNAs containing 5xe2x80x2 and/or 3xe2x80x2 transcriptional control regions, noncoding sequences of exons, introns or the like, in addition to regions encoding amino acids. Such sequences which do not encode any amino acids are also quite useful, for example, in developing a medicine using antisense techniques described hereinafter.
The 8th embodiment of the present invention is an expression plasmid which expresses either the gene of the 1st, 2nd, 3rd or 5th embodiment, or DNA of the 7th embodiment of the present invention. The 9th embodiment of the present invention is a transformant transformed with the expression plasmid of the 8th embodiment. Furthermore, the 10th embodiment of the present invention is a process for producing a recombinant protein which process comprises culturing the transformant of the 9th embodiment and recovering the recombinant protein expressed. As described above in the section of the 4th embodiment of the present invention, methods of preparing an expression plasmid and a transformant, and methods of producing a recombinant protein, per se, are all well known to those skilled in the art.
The 11th embodiment of the present invention is a peptide comprising at least 6 amino acids of a protein of the 4th or 6th embodiment of the present invention. In this context, the limitation xe2x80x9cat least 6 amino acidsxe2x80x9d is based on the fact that a minimal size of peptide capable of forming a stable structure consists of 6 amino acids, and preferred peptides are those consisting of 8 or more amino acids, more preferably of about 10-20 amino acids. A short peptide such as those consisting of about 10-20 amino acids can be synthesized on a peptide synthesizer, while a longer peptide can be obtained by preparing DNA through conventional genetic engineering, and expressing it in, for example, animal cells as described above. The peptide thus prepared can also be modified by conventional methods.
These peptides can be applied to pharmaceutical agents described hereinafter in the section of the 12th and 13th embodiments, and can also be used for producing antibodies.
The 12th embodiment of the present invention is a peptide of the 11th embodiment of the present invention which promotes neurite outgrowth. Such polypeptide may be prepared by the methods described above in the section of the 11th embodiment of the present invention. The promotion effect on neurite outgrowth can also easily be measured as described above in the section of the 5th embodiment of the present invention by adding Semaphorin Y to an activity assay system described above in the section of the 1st embodiment of the present invention and further adding thereto a test substance (i.e., a candidate peptide of Semaphorin Y). For details, see the descriptions in the section of the 18th embodiment of the present invention.
Specific examples of these peptides may be peptides which have lost the neurite-outgrowth inhibition activity of Semaphorin Y. A peptide lacking Semaphorin Y activity is expected to exert its neurite-outgrowth promotion effect, when it binds to receptors for Semaphorin Y or to Semaphorin Y itself, by inhibiting the binding of Semaphorin Y to the receptors. Some of such peptides will serve as CNS-neuron regeneration promoters as described hereinafter in the section of the 21st embodiment.
The 13th embodiment of the present invention is a peptide of the 11th embodiment of the present invention, characterized in that it contains the aspartic acid residue at position 198 of the amino acid sequence shown in SEQ ID NO: 6 or an amino acid residue corresponding to the position of said aspartic acid residue. Such peptides may be prepared by the methods described above in the section of the 11th embodiment.
As described above in the section of the 1st embodiment of the present inventions, the aspartic acid residue at position 198 of human Semaphorin Y shown in SEQ ID NO: 6 (in the case of rat, the aspartic acid residue at position 197) seems essential for expression of the activity of Semaphorin Y. Since this amino acid residue may possibly be involved in the binding between Semaphorin Y and its receptors, a peptide of this embodiment containing this amino acid residue may interfere the neurite-outgrowth inhibition activity of Semaphorin Y by binding to receptors for Semaphorin Y or to Semaphorin Y itself, resulting in promotion of neurite outgrowth. Some of the peptides having such effect will serve as CNS-neuron regeneration promoters as described hereinafter in the section of the 21st embodiment. Such neurite-outgrowth promotion activity can easily be measured as described above in the section of the 5th embodiment of the present invention by adding Semaphorin Y to an activity assay system described in the section of the 1st embodiment of the present invention, and further adding thereto a test substance (i.e., a candidate peptide of Semaphorin Y). For details, see the descriptions in the section of the 18th embodiment of the present invention.
In this embodiment, xe2x80x9can amino acid corresponding to the position of said aspartic acidxe2x80x9d refers to an amino acid residue which is located at the position corresponding to position 198 in human Semaphorin Y, when the amino acid sequence of the protein of the 4th or 6th embodiment of the present invention is aligned with the amino acid sequence of human Semaphorin Y shown in SEQ ID NO: 6 so as to give the maximum identity. Accordingly, xe2x80x9ca peptide characterized in that it contains an amino acid corresponding to the position of said aspartic acidxe2x80x9d refers to a peptide which comprises such amino acid at the position corresponding to position 198 in human Semaphorin Y as well as flanking amino acids on either side thereof.
The 14th embodiment of the present invention is an antisense nucleotide, or chemically modified variant thereof, which is directed against a segment comprising at least eight or more bases in the gene of any one of the 1st to 3rd embodiments, or in DNA of the 7th embodiment of the present invention.
As used herein, xe2x80x9cantisense nucleotidexe2x80x9d refers to a so-called antisense oligonucleotide, antisense RNA, or antisense DNA, and it may be artificially prepared using a DNA synthesizer, or may be obtained by, for example, expressing a gene in the direction opposite to the usual case (i.e., in the antisense direction). For details, see the descriptions in the section of the 21st embodiment of the present invention.
These antisense nucleotides are used for inhibiting the expression of Semaphorin Y as described hereinafter in the section of the 15th embodiment of the present invention, and are also useful as laboratory reagents for, for instance, in situ hybridization. In the present invention, xe2x80x9ca chemically modified variantxe2x80x9d specifically refers to such a variant that is chemically modified so as to enhance the transferability of the antisense nucleotide into cells or the stability of the antisense nucleotide in the cells. Examples of such chemically modified variant are phosphorothioate, phosphorodithioate, alkylphosphotriester, alkyl phosphonate, alkyl phosphoamidate and the like derivatives (xe2x80x9cAntisense RNA and DNAxe2x80x9d, WILEY-LISS, 1992, pp. 1-50, J. Med. Chem., 36, 1923-1937 (1993)). The chemically modified variant may be prepared according to, for example, the references cited just above.
The 15th embodiment of the present invention is an antisense nucleotide, or chemically modified variant thereof, of the 14th embodiment described above, characterized in that it inhibits the expression of the protein of the 4th embodiment of the present invention.
mRNAs produced by usual gene transcription are sense-strands, and the antisense nucleotides or chemically modified variants thereof can bind to such sense-strand mRNAs in cells to inhibit the expression of those particular genes. Therefore, the above-described antisense nucleotides or chemically modified variants thereof can inhibit the expression of Semaphorin Y, and can thereby inhibit the activity of Semaphorin Y. Some of antisense nucleotides or chemically modified variants thereof having such effect will serve as CNS-neuron regeneration promoters as described hereinafter in the section of the 21st embodiment of the present invention.
It can easily be determined whether a particular antisense nucleotide prepared, or a chemically modified variant thereof, has a desired inhibitory effect or not, by directly introducing the antisense oligonucleotide itself or by introducing a gene which produces said antisense RNA when transcribed, into cells expressing Semaphorin Y, and then determining whether the amount of the expressed Semaphorin Y is decreased or not.
Examples of antisense nucleotide having such inhibitory effect are those oligonucleotides having sequences complementary to either the coding region or the 5xe2x80x2 noncoding region of Semaphorin gene of the above-described embodiments. Especially preferred are those antisense nucleotides having sequences complementary to the transcription initiation site, translation initiation site, 5xe2x80x2 noncoding region, exon-intron junction region, or 5xe2x80x2 CAP region.
The 16th embodiment of the present invention is an antibody against the protein of the 4th or 6th embodiment, or against the peptide of any one of the 11th to 13th embodiments. Such antibody can easily be produced by using mouse or rabbit according to the procedures described in, for example, xe2x80x9cCurrent Protocols in Immunologyxe2x80x9d, pp. 2.4.1-2.6.6 (1992, J. E. Coligan ed.). Monoclonal antibodies can also easily be produced by the methods described in the above-mentioned reference. Such antibodies may be used in affinity chromatography or screening of cDNA libraries, and as pharmaceutical or diagnostic agents, or laboratory reagents. Some of such antibodies have the activity of neutralizing Semaphorin Y. Such neutralizing activity can easily be determined, as described above in the section of the 5th embodiment of the present invention, by adding Semaphorin Y to an activity assay system described in the section of the 1st embodiment of the present invention, and further adding thereto a test substance (i.e., a candidate antibody against Semaphorin Y). Some of such neutralizing antibodies will serve as CNS-neuron regeneration promoters as described hereinafter in the section of the 21st embodiment of the present invention.
The 17th embodiment of the present invention is a pharmaceutical agent comprising, as an active ingredient, any one of all of the genes (DNAs), proteins, peptides, antisense nucleotides or chemically modified variants thereof, and antibodies of the present invention.
Among such pharmaceutical agents, CNS-neuron regenerators and neurite-outgrowth inhibitors for PNS-neuron will be described in the sections of the 21st and 22nd embodiments of the present invention, respectively. See, therefore, the sections of the 21st and 22nd embodiments for such applications.
It is being demonstrated in recent years that certain Semaphorins play important roles not only in the nervous system but also in non-nervous system. For example, it has been suggested that Semaphorin may probably act in inhibiting the growth of cardiac muscles (Nature, 383, 525-528 (1996)). Also in the immune system, certain Semaphorin has been suggested to be involved in aggregation and survival of B lymphocytes (Proc. Nat. Acad. Sci. USA, 93, 11780-11785 (1996)). It has also been suggested more recently that a certain Semaphorin may play some role in the immune reactions in rheumatism (B.B.R.C., 234, 153-156 (1997)). Furthermore, involvement of Semaphorins in lung cancer has also been suggested (Proc. Natl. Acad. Sci. USA, 93, 4120-4125 (1996)).
Accordingly, Semaphorin Y of the present invention or its modified proteins, peptides, antisense nucleotides and the like are expected to be useful as antiallergic agents, immunosuppressive agents, or anti-tumor agents. For specific directions for use, dosage and the like, see the sections of the 21st and 22nd embodiments.
The 18th embodiment of the present invention is a method of screening for Semaphorin Y antagonists, characterized in that it employs the protein of the 4th embodiment of the present invention. As used herein, xe2x80x9cSemaphorin Y antagonistxe2x80x9d refers to a substance which inhibits, for example, the neurite-outgrowth inhibition activity of Semaphorin Y.
The screening is conducted by adding Semaphorin Y to an assay system for Semaphorin Y activity described in the section of the 1st embodiment of the present invention, and further adding thereto a test substance. In particular, inhibition of the Semaphorin Y activity resulted from the addition of the test substance to the culture medium throughout the incubation period or only temporarily in the incubation period can be used as an indicator in the Semaphorin Y activity assay conducted with added Semaphorin Y. It is also important to confirm that the test substance alone does not influence the survival and neurite-outgrowth of neurons at the same concentration. When both of these requirements are fulfilled, one can consider the test substance as a Semaphorin Y antagonist. Although it is preferred to prepare in advance the test substance in the form of aqueous solution, an organic solvent such as DMSO may also be used as a solvent. In any cases, it is important to minimize the volume of solvent so as to exclude any effects of the solvent on neurons. Specifically, the volume to be added should be less than an equal volume, preferably less than {fraction (1/10)} volume, and more preferably less than {fraction (1/100)} volume relative to the culture medium. Some of Semaphorin Y antagonists thus obtained will serve as CNS-neuron regeneration promoters as described hereinafter in the section of the 21st embodiment of the present invention.
The 19th embodiment of the present invention is Semaphorin Y antagonist obtained by the screening method of the 18th embodiment of the present invention. Such antagonist may have any structure and any form, provided that it inhibits the activity of Semaphorin Y.
The 20th embodiment of the present invention is Semaphorin Y antagonist of the 19th embodiment which comprises the protein of the 6th embodiment, the peptide of any one of the 11th to 13th embodiments, or the antibody of the 16th embodiment of the present invention. In other words, it is a protein of the 6th embodiment, a polypeptide of any one of the 11th to 13th embodiments, or an antibody of the 16th embodiment of the present invention which has an effect of inhibiting the activity of Semaphorin Y. Such antagonists can be identified by subjecting the above substances to the screening system of the 18th embodiment of the present invention, and some of the antagonists thus identified will serve as CNS-neuron regeneration promoters as described below in the section of the 21st embodiment of the present invention.
The 21st embodiment of the present invention is a CNS-neuron regeneration promoter, characterized in that it contains at least one of the antisense nucleotides or chemically modified variants thereof of the 14th or 15th embodiment, or Semaphorin Y antagonists of the 19th or 20th embodiment of the present invention. Since this embodiment relates to the use of substances in xe2x80x9cregeneration therapy for CNS-neuronxe2x80x9d, specific directions for use, dose and the like, of the substances are described below.
1) Antisense Nucleotide or Chemically Modified Variant Thereof
Application of antisense nucleotides has been attempted in various diseases, and in recent years, it is also considered to be applicable in neurological disorders (TINS 20, No. 8, 321-322 (1997)).
As described above in the section of the 14th or 15th embodiment of the present invention, the antisense nucleotide or chemically modified variant thereof of the 14th or 15th embodiment of the present invention can be used for inhibiting expression of Semaphorin Y gene. Accordingly, such antisense nucleotide may decrease the abundance of the Semaphorin protein, and promote regeneration of CNS-neurons. Therapeutic methods using the nucleotide or the variant include those in which the antisense oligonucleotide or its chemically modified variant itself is administered, and those in which antisense RNA is produced in cells.
In the method in which the antisense oligonucleotide or its chemically modified variant is administered as such, a preferred antisense oligonucleotide has a length, for example, about 5-200 bases, more preferably 8-25 bases, and especially preferably 12-25 bases. Antisense oligonucleotide or its chemically modified variant may be formulated by mixing it with stabilizing agent, buffer, solvent and the like prior to its administration. Such formulation may be co-administered with, for example, an antibiotic, anti-inflammatory, or anesthetic agent. Although the formulation thus prepared may be administered via various routes, it is preferred to topically administered at a site in which neurons are notably disordered. Usually, regeneration of neuron takes several days to several months, and the formulation is administered every day or every several days to several weeks during the period. To avoid such frequent administrations, a sustained-release mini-pellet formulation may be prepared and embedded near the affected site. Alternatively, a formulation may be gradually and continuously administered to the affected site by means of, for example, an osmotic pump. The dose is typically adjusted so that the concentration at the site of action will be 0.1 nM to 10 xcexcM.
In the method in which antisense RNA is produced in cells, a preferred antisense RNA has a length of, for example, more than 100 bases, preferably more than 300 bases, and more preferably 500 bases or more.
The methods by which a gene expressing an antisense RNA is introduced into a patient include an in vivo method in which the gene is directly introduced into cells in a living body, and an ex viva method in which the gene is introduced into particular cells ex vivo and the cells are returned into the body (Nikkei Science, April, 1994, pp. 20-45; Gekkan-Yakuji, 36 (1), 23-48 (1994); Jikkenn-Igaku-Zokan, 12 (15), 1994; and references cited therein). An in vivo method is more preferred.
Such in vivo methods include a method employing recombinant viruses and other methods (Nikkei Science, April, 1994, pp. 20-45; Gekkan-Yakuji, 36 (1), 23-48 (1994); Jikken-Igaku-Zokan, 12 (15), in its entirety (1994); and references cited therein).
The methods employing recombinant viruses may include the methods in which Semaphorin gene is incorporated into a virus genome of, for example, retrovirus, adenovirus, adeno-associated virus, herpesvirus, vaccinia virus, poliovirus, or sindbis virus, and the recombinant virus is introduced into a living body. Among these methods, those employing retrovirus, adenovirus or adeno-associated virus are particularly preferred.
Other methods may include a liposome method or a lipofectin method. The liposome method is particularly preferred.
For the ex vivo methods, a micro-injection method, the calcium phosphate method, electroporation and the like may also be used, besides those techniques described above.
Administration of the gene to a patient is carried out via appropriate routes depending on particular disease or symptom to be treated, and the like. For example, it may be administered intravenously, intraarterially, subcutaneously, or intramuscularly, or directly administered into an affected site such as neuron. For example, when spinal cord is infected with the recombinant viruses, the expression of Semaphorin gene is inhibited exclusively in the spinal cord. Expression of antisense oligonucleotide of the present invention typically lasts several days to several months, and such single infection is sufficient to allow regeneration of neuron. The gene may also be re-infected, when weakly expressed. When administered by an in vivo method, the gene may be formulated in the form of, for example, a solution, and typically it is formulated in the form of an injection containing Semaphorin gene as an active ingredient to which conventional carrier and the like may be added, if necessary. In the case of liposomes or membrane-fused liposomes (such as Sendai virus (HVJ)-liposomes) containing Semaphorin gene, the liposome preparations may be in the form of a suspension, a frozen preparation, a centrifugally-concentrated frozen preparation or the like.
Although the amount of Semaphorin gene in the formulation may vary depending on the disease to be treated, the age and weight of the patient, and the like, it is typically 0.0001-100 mg, and preferably 0.001-10 mg, and such formulation is preferably administered once every several days to several months.
2) Modified Protein of Semaphorin Y
As described above in the sections of the 5th and 6th embodiments of the present invention, one can prepare a modified Semaphorin Y of which neurite-outgrowth inhibition activity on CNS-neuron has been eliminated. When administered into a living body, such modified protein is expected to bind to receptors for Semaphorin Y in place of Semaphorin Y, resulting in inhibition of Semaphorin Y activity and promotion of regeneration of CNS-neuron.
Such modified protein of Semaphorin Y is formulated with stabilizer, buffer, and diluent, and administered to a patient for therapy. Such formulation may be administered via various routes, and it is preferred to topically administer to the focal site. Since regeneration of neuron typically takes several days to several months, the formulation is administered once or more in order to continuously inhibit Semaphorin Y activity throughout the period. When administered more than once, it is desirable to administer it every day or repeatedly at appropriate intervals. When administered to CNS by injection, for example, into spinal cord, several hundreds xcexcg to 2 g, preferably less than several tens mg, are used per administration. To reduce the administration frequency, it may be administered using a sustained-release formulation or gradually administered over a long period by means of, for example, an osmotic pump. Alternatively, it may be administered by grafting cells expressing such modified Semaphorin Y protein into a living body.
3) Peptide of Semaphorin Y
Some of the peptides of any one of the embodiments from 11th to 13th of the present invention suppress the neurite outgrowth inhibition activity of Semaphorin Y on CNS-neuron by inhibiting the binding of Semaphorin Y to its receptors, resulting in promotion of CNS-neuron regeneration. Examples of peptide having such effect include a peptide characterized in that it contains aspartic acid residue at position 198 of human Semaphorin Y shown in SEQ ID NO: 6 or an amino acid residue at the position corresponding to that of said aspartic acid residue, as described above in the section of the 13th embodiment of the present invention. The suppression may be any one of competitive, noncompetitive, uncompetitive, and allosteric inhibitions.
As for the methods of formulating or administering such polypeptides, and their doses, see the above section xe2x80x9c2) Modified protein of Semaphorin Yxe2x80x9d.
4) Antibody Against Semaphorin Y
A neutralizing antibody which neutralizes the activity of Semaphorin Y is expected to promote the regeneration therapy of CNS-neuron by inhibiting Semaphorin Y activity, when administered into a living body.
The methods of formulating or administering such neutralizing antibodies and their doses may be the same as described in the above section xe2x80x9c2) Modified protein of Semaphorin Yxe2x80x9d. Alternatively, a method in which cells producing a monoclonal antibody are grafted directly into CNS may also be used, as described in Nature, 343, 269-272 (1990).
The 22nd embodiment of the present invention is a neurite outgrowth inhibitor for PNS-neuron, characterized in that it contains at least one of the proteins of the 4th embodiment of the present invention. Although the proteins of the 4th embodiment of the present invention may inhibit the neurite outgrowth of CNS-neuron, they are also expected to inhibit the neurite outgrowth of PNS-neuron, since PNS-neuron also probably expresses receptors for Semaphorin Y, and receptors for other Semaphorins also probably react with Semaphorin Y. Accordingly, they may serve as therapeutic agents for atopic dermatitis, pain or other diseases by virtue of their inhibition activity on neurite outgrowth of PNS-neuron.
As for the methods of formulating or administering such proteins, and their doses, see the above section xe2x80x9c2) Modified protein of Semaphorin Yxe2x80x9d.
The 23rd embodiment of the present invention is a transgenic animal in which either the gene of any one of the 1st to 3rd and 5th embodiments, or DNA of the 7th embodiment of the present invention has been artificially inserted into its chromosome, or has been knocked out.
As apparent from the following references, one skilled in the art can quite easily produce a transgenic animal which expresses the gene of the 1st, 4th, 7th, or 9th embodiment of the present invention, in the light of the gene information on Semaphorin Y of the present invention: xe2x80x9cManipulation of Mouse Embryoxe2x80x9d edited by B. Hogan et al., 1986, Cold Spring Harbor Laboratory; Shinichi Aizawa, xe2x80x9cGene Targetingxe2x80x9d, 1995, Yodosha, etc. Accordingly, the transgenic animal thus produced is naturally included within the scope of the present invention. The transgenic animal thus produced is very useful as an animal model for developing pharmaceuticals or as an animal used for screening of pharmaceuticals. Furthermore, a so-called knockout animal in which the gene of the 1st, 4th, 7th, or 9th embodiment of the present invention has been deleted is characterized in that it does not contain such gene. As described in literatures, or as apparent from the common knowledge in the art, such knockout animals cannot be produced without the gene information on Semaphorin Y of the present invention. It goes without saying, therefore, that such knockout animals are included within the scope of the present invention.
While Semaphorin Y has an important in vivo function relating to regeneration of neurons as described above, it has been also suggested as mentioned above that Semaphorin Y may have other unknown functions such as immunosuppression (Cell, 75, 1389-1399 (1993)). Accordingly, it is quite important to investigate the expression of Semaphorin Y gene or the distribution and function of Semaphorin Y protein for studying this technical field or for diagnosing patients with neurological disorders or other diseases. The present invention can also provide gene probes, antibodies, recombinant proteins, transgenic animals and the like which can be used for such purposes.